2-Oxoglutarate (2OG) is a precursor for neurotransmitter glutamate, and an important metabolic intermediate for maintaining the capacity of the Krebs cycle in glutamatergic neurons. 2OG enters neuronal cells through a high affinity uptake system localized to glutamatergic neurons. This uptake system is under negative feedback control by glutamate, biphasic modulation by glutamine (another source for neurotransmitter glutamate) and positive modulation by a putative novel protein, transport activating factor (TAF). TAF accelerates 2OG uptake by several hundred percent. We propose to purify, partially sequence, clone, and raise antibodies to TAF from bovine retina. The results of this investigation will characterize a hormone of significance to neural systems in general but especially to the retina, which has a very high metabolic rate as well as a robust glutamatergic neurotransmission system.